You tell me, how many? Because to my knowledge, there's just one asynchronous IO interface Linux and it's Linux-AIO as used via io_setup()/io_submit()/io_getev

You tell me, how many? Because to my knowledge, there's just one asynchronous IO interface Linux and it's Linux-AIO as used via io_setup()/io_submit()/io_getevents()/io_destroy() w/O_DIRECT. There's glibc support for POSIX AIO, but that's not some kernel feature, it's just POSIX support and not especially great. I'm inclined to suspect you're confusing asynchronous IO with the myriad file descriptor event multiplexing interfaces: select()/poll()/epoll_wait(), which are orthogonal to this.